Fatestay Night Self-insert
by Canis Lupus 54
Summary: Exactly what it says on the tin.
1. Chapter 1

I materialized in the shed. I looked at the red haired boy who had summoned me. I glanced at the blue-haired, blue –clad man standing opposite him.

I charged the latter, swinging my invisible sword, forcing the man out of the shed and creating a huge wave of air pressure.

I turned to the boy, who was looking confusedly at me. I checked my chest and my crotch and found that something was wrong with both.

I exited the shed and resumed my attack. With skills I shouldn't have had I struck blow after blow after blow. I blocked every counter, parried every strike. I struck with mana enhanced power, overpowering my opponent. Finally, we broke apart, eyeing each other.

"What do you say we just call a draw for tonight?" Lancer asked.

"Sounds good," I said.

"Well, then—Wait, really?"

"Yeah, I have stuff to get sorted out. Go, shoo."

"Well, um, thanks, Saber. See you around, I guess."

"No problem."

I walked back over to Shirou.

"Hi, you probably have a lot of questions," I said. "You're part of a sort of game called the Holy Grail War. This is responsible for the gas leaks and murders recently. I'm King Arthur, but you should call me Saber. Except I'm actually a guy from a universe where this is all a visual novel in King Arthur's body. Yes, King Arthur was a girl. Questions answered?"

"More or less," said Shirou, "but how do I win the Holy Grail War."

"Hold on, Rin and Archer are approaching. Follow me."

I jumped over the wall and approached Archer and Rin with a relaxed posture, trying to appear visibly non-threatening.

"Yo, I'm Saber," I said, "Shirou is kind of clueless, so please help us out for right now."

Shirou then emerged from the house behind me.

"Tohsaka!" he said.

"Good evening, Emiya-kun,"

"Wait, one thing," I said, then I stabbed Archer in the chest, "he's Shirou from the future and would try to kill Shirou if I didn't wound him. At least, I think that's how it works."

"Shirou, your Servant is weird," Rin said.

"Hey!"

"Can someone explain all this Servant and Holy Grail War stuff?" Shirou asked.

"Sure. Rin, lead the way to the Kotomine Church."

"How do you—"

"I'll explain on the way."

I watched Shirou and Rin walk down from the Kotomine Church, joining them as they passed. I was wearing the large rain poncho Saber wore in this scene. Shirou and Rin had confused and incredulous looks on their faces, respectively.

"So," Rin said, "you're saying you're from another universe, where all of this is fictional, and you're here because you fell asleep watching a show about the last Grail War"

"Yes," I replied.

"So, where's the real Saber?"

"I don't know, maybe she's still here, I have her sword skills after all."

"Interesting."

"So, Rin how about we team up,"

"Sounds good. I could use your foreknowledge."

"Okay, let's get ready for Berserker's attack."

"Too late, Saber! Good evening, Onii-chan!" said Illya, "I'm Illyasviel von Einzbern. You can call me Illya."

"Crap, we're screwed."

I charged at Berserker, and jumped over his head. I turned around and slashed at his back. It didn't do much.

 _Okay , new plan._

Berserker whirled around and struck me with his axe-sword. I slammed into the wall on the side of the path, then fell to the ground.

"Saber!" Shirou said.

As I struggled to stand, Shirou ran up and pushed me out of the way of the next blow, taking it himself.

Berserker and Illya then left.

"I wanted to avoid this, but he'll be fine," I said, "Help me carry him home."

"Okay," Rin said.

We carried Shirou home. Rin and I went to sleep.


	2. Chapter 2

"Shirou, I have something important to tell you," I said.

"What?"

"When I first saw that, I thought it was kind of dumb. Seeing it in person did not improve my opinion."

"What was I supposed to do, let you die?"

"You realize I'll disappear if you die, right? You could've been killed. Not many people know this, but people die when they are killed."

Shirou looked down.

"Look, I know you don't value your own life, but just try not to let yourself be killed anymore."

"How am I alive anyway?"

"My sword's magic sheathe is inside of you, you can keep it for now, but I have plans for it later. Let's have a strategy meeting after breakfast."

At breakfast my presence was explained the same way it was in the original anime. I knew Sakura saw right through the excuse, but it was too early to bring her on the team. First we had to take down Rider, then Caster and Assassin, Berserker and Lancer were last. Then Gilgamesh. That was going to be fun.

After breakfast we held our strategy meeting.

"So, Saber, what's our first move?" asked Rin.

"Today at school you might hear a scream. This is going to lead into a confrontation with Rider. I need directions to the school so I can help."

"I have a question," Shirou said, "How is there a place where all this is fictional? And if it exists how are we real?"

"Ever heard of the Many Worlds Interpretation?"

"No…"

"Well, basically it says there are infinite universes, which means that by sheer probability if nothing else, all fiction is real, and everything real is fictional, get it?"

"More or less. What brought you here?"

"Well, cross universal fanifics always seem to mention some Zelretch guy, but I don't really know who that is. Maybe he did something. Anyway, one of you write down directions to school then off you go."

That evening I went to the school. I heard Shirou scream in pain and rushed toward the sound. I saw Rider hoisting Shirou up a tree. I quickly jumped up and removed the spike from his arm. Rider wrapped the other chain around my free hand and pulled. I jumped toward Rider, throwing the woman, expecting resistance, off balance. I punched Rider in the face, then summoned my sword and struck. Rider blocked but was forced backwards. So I struck again and again. The third time Rider's guard broke, so I stabbed her in the stomach. She jumped backwards and we warily eyed each other.

"Don't worry," I said, "I have a plan to help Sakura, Medusa."

Rider was caught off guard and I took advantage of that. With her off guard, I used Invisible Air to boost my speed and bisected Rider.

"Okay," I said to Shirou, "that's one down."

Then I yelled, "Shinji get out here!"

With a squeal of fear, Shinji appeared from behind a tree.

"Shinji, is there a Servant at Ryuudou Temple?" I asked holding my sword to his throat.

"Y-y-y-y-yes, how did you know?"

"I have my ways. You can go, but never touch Sakura again. If you do and I find out, it will be extremely painful, for you."

"O-okay, can I go now?"

"Sure."

"Let's visit that temple tomorrow."

"Okay, let me check on the girl Rin was with."

"Okay, see you at home."

Then I went home.


	3. Chapter 3

That evening we had another strategy meeting.

"You're awfully calm for someone in your situation," commented Rin.

"What would freaking out get me?" I asked.

"Good point."

"Any way, here's our strategy for taking down Caster and Assassin: Archer and I are going to attack them together. That's pretty much it. I know I can beat Assassin alone and together we can definitely beat Caster and Kuzuki."

"Wait, Kuzuki-sensei?"

"Yes, he's Caster's Master. Anyway, meanwhile, Shirou should practice swordsmanship with me and projection magic. Afterwards we'll take on Berserker. Shirou, if you see a sword in your dreams, be ready to project it. Any objections?"

There were none.

The next day, Archer and I travelled to Ryuudou Temple.

"Good evening," said Assassin, "My name is—"

"Hi, Sasaki-san!" I said cheerfully, "Let's just fight."

Assassin's eyes widened in surprise but he quickly recovered. He stepped forward and struck with impossible speed, and I blocked with equal speed. We clashed repeatedly. Eventually, we held a clash for a while, both trying to gain the advantage. My strength was superior, so I pushed through and forced him back.

"Show me, your true sword, Saber!" he said.

"Okay."

"Well then, I'll show you mine—Wait really?"

"Yeah, there's a little bit of buildup though, so just wait right there."

"Okay, I eagerly await the clashing of our secret techniques."

A tornado started around me as my sword started glowing. Assassin watched intently. That is, until an arrow pierced his skull. And exploded.

"Thanks, Archer," I said.

"No problem," Archer said.

We walked up the path through the gate.

"I don't know exactly where in the temple they are, do you remember?" I said.

"No, we'll have to look around."

"Okay."

So we looked around. Eventually, we found Caster and Kuzuki.

Archer fought Kuzuki and easily killed him. He then joined me fighting Caster. Not being suited to direct combat, Caster quickly fell. Archer and I talked as we walked home.

"I could just astralize and fly home," said Archer.

"So why don't you? Anyway, are you still planning on killing Shirou?"

"Not sure yet. I'm clearly in a different timeline than my own, so killing him wouldn't help me any, but I can still save him from himself."

"I'd really rather you not. Don't make things harder for me. He may not walk your path. It's rather selfish to kill him because of what might be."

"I think I've earned a little selfishness."

"Just think about it, okay?"

"Okay."


	4. Chapter 4

"Now that Assassin is dead," I said, "We're going to have to kill Zouken Matou. I don't want to risk him summoning True Assassin."

"True Assassin?" Rin asked.

"Hassan-I-Sabbah," I explained.

"Who's that," Shirou asked.

"The leaders of the Hashashin, a group whose name became the word assassin, the word assassin acts like a catalyst to summon them. It started as a name, but became a title. There were nineteen Hassan-I-Sabbahs. They're all virtually identical and their Noble Phantasms have the same name, so the only way to differentiate them is to see them in action."

"Sounds like trouble."

"So, what's your plan?" asked Rin.

"First we need to have Shirou project Avalon," I said.

"I think I can do that."

Shirou struggled to project Avalon for about half an hour before succeeding.

"Okay, now we wait for Sakura. Rin, prepare some healing magic."

The next day Sakura and Fujimura came for breakfast as Sakura was leaving, I asked her to wait.

"Hold this," I said, handing her Avalon.

Then I stabbed Sakura in the heart. I moved the sword around a little to make sure I got Zouken. I withdrew my sword.

"Rin, now!" I said.

Rin came in and healed Sakura partially. Avalon took care of the rest.

"Archer!" I said.

Archer traced Rule Breaker and stabbed Sakura. Once again Avalon healed the wound.

"Okay, it's done," I said.

"You couldn't have done that a different way to do that?" Sakura asked.

"Well, we would've had to find a surgeon with magical knowledge. This was far easier," I explained.

"So, Sakura's safe now, right?" Shirou asked.

"As long as Shinji keeps my threat in mind, yes."

"Good."

"Now all that's left is Berserker, Lancer, and Gilgamesh."

"Gilgamesh?" Rin asked.

"I'll explain when we get to him," I said, "Now, we're ahead of schedule so let's take a couple days to just have some fun."


	5. Chapter 5

The next day we went to the beach. Then we went to the movies. Then we had dinner. Sakura participated in all these activities. She seemed happy. I saw her and Rin talking at some points. I hoped they were making up. Then, on our way home, the worst possible thing happened.

"Hey brat, didn't anyone teach you not to take other people's things?"

 _Really?_ I thought _,_ _We're probably weeks before this is supposed to happen and he shows up with the exact same line?_

"Listen, Gilgamesh," I said, "I'm not 'your' Saber so shoo."

"You dare tell the King of Heroes to shoo?"

"Yes. Go. Now."

"I don't know who has possessed the body of Saber," said Gilgamesh, "but I cannot allow such disrespect. Gate of Babylon."

Swords and spears flew forth from the portals that opened. Archer materialized and countered with his own barrage of weapons. I charged Gigamesh. He drew a sword from a portal and parried my first strike, but with my second I broke the sword and forced him back. I continued my attack, disarming the King of Heroes time and time again, only for him to arm himself again. Archer attacked from behind, but a barrage of weapons forced him away. He tried to take a shot but his arrow was stopped before it ever reached the Golden King. I came to the conclusion that I would have to use Excalibur with perfect timing to defeat Gilgamesh.

Then, a bunch of weapons and gems hit Gilgamesh, creating an explosion. I looked to see that Shirou and Rin had joined the fight.

"Think you can beat us all, Gilgamesh?" I asked.

"Easily," Gilgamesh said.

He withdrew Ea from the Gate of Babylon. He jumped back, trying to get an angle he could hit us all from. I charged, I had to end this now.

"Saber!" I heard Shirou shout.

"Enuma—"

"Ex—"

"—Elish!"

"—calibur!"

The two blasts collided with barely any space between us. I knew it was only a matter of time before Ea overwhelmed Excalibur. Then, an arrow flew toward Gilgamesh's head. He dodged at the last second but his focus was disrupted. Excalibur overpowered Ea and struck Gilgamesh. Though his Noble Phantasm absorbed the brunt of the blast, he was still hurt. He quickly left.

Then, I collapsed.


	6. Chapter 6

I awoke in the Emiya Estate shortly afterwards. I looked around. I was alone in my room. I got up, quietly opened the door, noted that it was morning, and walked toward the dining room.

Shirou, Rin, and Archer were gathered around the table. They were talking.

"I'm worried about Saber," said Shirou, "What's wrong with her?"

"Assuming you're talking about why she collapsed, she used most of her mana using her Noble Phantasm. Your link to her is incomplete, so she can't get more like a Servant normally would."

"Isn't there any other way to replenish her mana?"

"Well, you could use a Command Seal to have her attack people and consume their mana."

"I'd never do that! Archer, you're future me, don't you know how to deal with this."

"He does," I interrupted, "But it's a little embarrassing."

Shriou and Rin nearly jumped out of their skins. Archer merely turned slightly to put me in his view, eyes widened slightly in surprise.

"Someone's feeling better," he said.

"Do you have Presence Concealment?" asked Rin.

"Saber, you're okay!" said Shirou.

"I wouldn't say I'm okay," I said, "I'm still low on mana and if I try to fight I'll disappear. Fortunately, I know of two ways to restore my mana. Magic Circuit transfer and a tantric ritual."

"I've mever heard of magic circuit transfer," said Rin.

"Neither have I," said Archer.

"Crap," I said.

"What, why crap? What's a tantric ritual?" asked Shirou.

"We have to have sex."

"What!?"

"This is going to be awkward. Wait! I just remembered, we traced Avalon. It can restore my mana, so we don't have to have sex."

"I was wondering when you were going to remember that," said Archer.

I retrieved Avalon, sheathed Excalibur in it, and returned to the dining room.

"I should be good now," I said, "Now, we have to focus on protecting Illya."

"What?" said Rin, "She tried to kill us!"

"I know, and we might have to defeat Berserker first, but Gilgamesh and Kirei are going to try to use her to summon the Holy Grail."

"That reminds me, why is Gilgamesh here?"

"He was the last war's Archer, who was granted a permanent body, at the cost of going mildly insane, not that he was a very good person to begin with. Actually, he was your father's Servant, Rin. But he ultimately betrayed your father."

"Oh…"

"Anyway, let's go to Illya's place and hopefully convince her to join us peacefully."

"Okay," said Rin and Shirou.

The four of us then prepared and headed to Illya's place. When we arrived we were greeted by the sounds of a battle inside.


	7. Chapter 7

We quickly headed inside, to be confronted with the sight of Gilgamesh and Berserker fighting. Berserker was clearly losing. With Mad Enchantment, his only available tactic was blindly charging forward. Illya was cowering behind Berserker as he soaked up Gilgamesh's onslaught of weapons.

I ran around the battle to Illya.

"Illya," I said, "You have to use a Command Seal to undo Mad Enchantment!"

"But…," Illya responded.

"He won't leave you, I promise. He'll protect you."

"Okay… Berserker, I order you to regain your sanity!"

Another wave of weapons flew toward Berserker, with a roar of determination, distinct from his earlier, bestial roars, he swung his axe-sword in a wide arc. The shockwave from the swing knocked every weapon out of the air. Then, in the blink of an eye Berserker was right in front of Gilgamesh, swinging his axe-sword. Gilgamesh's eyes widened and he leapt backwards, avoiding the strike, but not the shockwave that came with it. The shockwave sent him flying across the room, smashing into a wall.

Gilgamesh stood up, eyes full of rage, and spoke. I raced to stop him.

"Enki—," he said, and then I was there.

I drew Excalibur and struck. Gilgamesh hurriedly grabbed a sword from the Gate of Babylon and parried, but he was knocked off balance. I pressed the attack, landing a glancing blow on his cheek, back flipping to avoid his counter, and clashing with him once more. We clashed again and his sword broke. I struck again and he leapt back to avoid the strike, only to find himself backed up against the wall once more, with me on one side and Berserker on the other. He looked between us, evaluating the situation.

He apparently decided a retreat was in order, since his next action was to summon a golden sports car looking device from the Gate of Babylon and speed through a wall and into the forest.

"I must thank you properly later, King of Knights," Berserker said, "For now, can I trust you to watch Illya for me?"

"Of course," I replied.

"Then catch up when you can!"

"This is so awesome."

With that, Berserker sped off after Gilgamesh at full speed.

I ran over to Illya and examined her.

"Are you okay, Illya?" I asked.

"Yes, I'm fine,"

"What just happened?" asked Shirou.

"King Arthur and Hercules versus Gilgamesh is what just happened. And it was awesome," I said.

"No, I mean, did Gilgamesh just speed out of here in a Lamborghini?"

"Oh that. The Gate of Babylon houses the prototypes of all human accomplishment."

"I get it. Kind of."

"That aside," said Rin, "Berserker is Hercules!?"

"Of course!" boasted Illya, "He's the strongest Greek hero!"

"Out of all Servants, he probably stands the best chance of beating Gilgamesh one-on-one. Or he would if he was properly equipped, at least. Now let's go!" I said.

With that we ran off into the forest. Eventually, we reached the point where Berserker and Gilgamesh were fighting. Gilgamesh's car lay in a smoking ruin, upside down, resting against a tree.

We were at the river that divided Shinto and Miyama. A golden boat sat in the middle of the river, weapons occasionally flying from above the ship toward the shore, where Berserker stood, deflecting every weapon. I ran up to Berserker.

"Can't you jump over there?" I asked.

"I could," he said, "But I am no son of Poseidon. If I miss, it would not be pleasant."

"Got it. Archer," I said, "will you help us?"

"…Sure. I'll help," Archer said.

"Good, Shirou, trace a bow for Berserker. Archer and Berserker, keep Gilgamesh busy while I approach him on foot."

"Right," said Archer, Berserker, and Shirou.

Shirou traces a bow and some arrows and gave them to Berserker. Archer materialized his own bow and readied an arrow.

"Okay," I said, "let's go."

I jumped onto the river's surface and ran to Gilgamesh's boat. Weapons flew toward me, but each was deflected by an arrow. I jumped on board the boat, noted that Gilgamesh was breathing heavily, his armor dented and broken in spots, and blood pouring from several wounds, and performed a leaping slash at Gilgamesh. The force of the flow knocked him over, but he quickly regained his footing. I attacked again. He drew a sword from the Gate of Babylon and parried my blow. Gilgamesh leapt backwards and two arrows flew through where his head had been a moment before. I decided to end this now.

"Excalibur!" I exclaimed.

A golden laser erupted from by sword, tearing apart the boat and shooting toward Gilgamesh. He drew Ea.

"Enuma Elish!" he declared.

A red tornado of energy spiraled out from the sword and slammed into Excalibur, violently stopping it.

Over the roar of the attacks I heard Gilgamesh smugly declare, "This is boring."

With that, Ea overwhelmed Excalibur and I was sent flying off the boat. I righted myself in midair and landed on the water on my feet. Gilgamesh stood on the wreckage of his ship, glaring at me.

"You mongrels have now destroyed two of my treasures!" he declared, "I will make sure you pay."

Suddenly I heard two voices from the shore shout the same thing.

"Nine Lives!" They said.

Two hundred laser-like arrows flew toward Gilgamesh. He leapt into the air to avoid them, but they followed his movements, all two hundred arrows pierced him. He fell back down to the wreckage of his ship. Amazingly, he was still alive, as I saw him struggle to stand. Not for long.

"Excalibur!" I exclaimed.

The golden light that erupted from my sword vaporized Gilgamesh and his ship. I returned to the shore.

"Now," I said to Illya, "can we at least stay allies until we defeat Lancer and Kirei?"

"Hmm…, I guess so," said Illya.

Then the six of us returned to the Emiya Estate on foot together. Illya astralized Berserker when we arrived in town and we returned home.


End file.
